1. Field of the Invention
The present invention relates to control of miniature unmanned aircraft, wherein directional control is remotely controlled, and other aspects of flight such as instantaneous attitude and altitude conditions are automatically controlled from within the aircraft.
2. Description of the Prior Art
Small, unmanned aircraft operate under certain constraints imposed by the government. Aircraft weighing less than fifty-five pounds, not able to reach speeds of two hundred miles per hour, and having flight direction controlled from the ground need not be licensed by civil air authorities. Because small, unmanned aircraft are capable of many civilian uses in gathering aerial data and transmitting data, it is extremely desirable to use them in place of larger, manned aircraft which operate at much greater costs, are subject to severe restrictions, and are susceptible to creating much more severe hazards in the event of mishaps.
Small unmanned remotely controlled aircraft, popularly known as “model” aircraft, have been utilized by hobbyists for years. Such aircraft, when built to sufficient scale, would be adequate in some ways to play a role in data acquisition and transfer. However, traditional model aircraft are intended to be flown within a limited radius from a person controlling the aircraft, under visual line-of-sight control, and usually over areas dedicated to that purpose. Utilizing small, unmanned aircraft over greater areas, for example by radio line-of-sight, on missions demanding greater precision in flight control imposes demands which cannot be met by traditional model aircraft.
One severe problem is that of maintaining appropriate attitude. When, for example, taking a sequence of optical scans, such as multispectral “pushbroom” scans, the data becomes much more useful, or more immediately useful, if taken from the same vantage point. Otherwise stated, it is desirable to maintain the data acquisition platform at a constant orientation to the surface of the earth. This is next to impossible to accomplish if relying upon the “line of sight”, from the ground control methods of traditional model aircraft.
Constant orientation relative to the surface of the earth requires close control over both attitude and altitude of the aircraft. Flight control of aircraft could be entirely automated using sufficient sensors, combined with microprocessors and data inputs such as by the Global Positioning System (hereinafter, GPS) and by preprogrammed flight instructions. Particularly addressing civilian uses in the United States, it is highly desirable to have an unmanned aircraft which is light enough to avoid the fifty-five pound limit which is a threshold above which severe restrictions on use of an aircraft are imposed, and which cannot operate under sustained independent directional control. There exists a need art for aircraft which have minimized the burden of flight control imposed on external supervision by performing certain tasks internally, while still having directional control originating remotely, thereby avoiding undue restrictions on unmanned, miniature aircraft.